you are confusing mount....meaning make accessible....to a booted system with grub or lilo.
if you want to view or copy files you add lines to each system's fstab file for the relevant folder
eg if both are ext2 with su (root powers)
1) boot sles
edit Sles fstat to add one line
/dev/hda4 /mnt/bt ext2 users 0 0
2) boot bt....needs a grub entry in sles /boot/grub/menu.lst as above
edit BT fstat to add one line
/dev/hda6 /mnt/sles ext2 users 0 0
3) did you read my signature or not?
if grub is in mbr its the bootloader for sles....so you need to boot sles then using root powers to edits its bootloader grub file.